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Vintage IBM PCjr gets 3x to 6x speedup with FPGA-based 8088 microprocessor transplant. But why?

Xilinx Employee
Xilinx Employee
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As a winter-break project, Edward at MicroCore Labs ported his FPGA-based MCL86 8088 processor core to a vintage IBM PCjr. The MCL86 core combined with the minimum-mode 8088 BIU consumes 1.5% of the smallest Kintex-7 FPGA, the K70T. Four of the Kintex-7 FPGA’s 135 block RAMS hold the processor’s microcode. Edward disabled the cycle accuracy governor in the core and added 128Kbytes of internal RAM using the same Kintex-7 FPGA that he was using to implement the processor. The result: the world's fastest IBM PCjr running Microsoft DOS 2.1.




IBM PCjr sped up by Kintex-7.jpg



IBM PCjr sped up by a MicroCore Labs MCL86 processor core implemented in a Kintex-7 FPGA




Will the world beat a path to Edward’s door for fast antiquated personal computers? Probably not. The PCjr, code name “Peanut,” was IBM’s ill-fated attempt to enter the home market with a cost-down version of the original IBM PC. When it was announced on November 1, 1983, the entire market quickly developed a “Peanut” allergy. Adjectives such as “toylike,” “pathetic,” and “crippled” were used to describe the PCjr in the press.


The machine’s worst feature, the one to come under the most criticism, was its “Chiclet” keyboard (named after a chewing gum with a shape similar to the keyboard’s keys). IBM had gone from making the world’s best keyboard on the IBM PC to the world’s worst on the PCjr. After a year and a half of sales that dropped off a cliff as soon as the discounts ended, IBM killed the machine.


So what’s the point of MicroCore’s Franken-Peanut then?


It nicely demonstrates the vast implementation power of even the smallest Xilinx FPGAs. MicroCore Labs’ MCL86 processor core easily fits in low-cost FPGAs from the Spartan-6 and Spartan-7 product lines.


Finally, here’s a very short video of MicroCore’s jazzed-up IBM PCjr playing a little Bach:




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